That’s how close a Mountain View pilot calculated an Air Canada Airbus 320 came to striking the first of four fully-loaded passenger jets on a SFO taxiway Friday in one of the scariest close-calls aviation experts have ever seen.

“If you just sit there and count to 11 seconds, we’re not talking about a lot,” said Max Trescott, a general aviation pilot for more than 40 years and instructor at Palo Alto Airport. “That’s ridiculously close.”

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FlightAware, which monitors air traffic online, determined Air Canada flight 759 dropped to as low as about 175 feet on approach at SFO as the wayward pilot mistakenly headed for Taxiway C, instead of Runway 28R. Based on those figures, the plane’s speed at the time, and the positioning of the four planes awaiting departure on the taxiway, Trescott did some math.

“On a normal 3-degree glide slope, an aircraft descends 320 feet for every nautical mile flown,” Trescott explained in his blog Trends Aloft. “So at 175 feet, an aircraft would be 0.55 nautical miles from the touchdown zone. The typical landing speed for an A320 is around 130 knots to 140 knots. At 140 knots, an aircraft covers 2.33 miles per minute, so it could travel 0.55 nautical miles in a little over 14 seconds. Of course, if you figure a typical airliner is perhaps 40 feet high … then it would have been about 11 seconds to impact.”

The incident has set the international flying community abuzz and rightfully so, Trescott said.

“I would say this is quite alarming and uncommon to be this close,” he said. “That’s relatively rare.”

Another aviation expert said this could have triggered the greatest aviation disaster in history with almost 1,000 passengers on all five airplanes involved; four of the aircraft awaiting takeoff filled with fuel.

Pilots receive NOTAMS — notices to pilots — regularly alerting them to closed runways or other changes in normal flight procedures, and Air Canada would have dispatchers alerting their pilots of a closed runway, Trescott said.

SFO spokesman Doug Yakel said that Runway 28L closed down at 10 p.m. Friday, about two hours before Air Canada was scheduled to land. A NOTAM was sent alerting pilots of the closure until 7 a.m. Saturday, and the airport had a large, flashing “X” at the landing area to reinforce the closure, he said.

The FAA and NTSB, which have launched investigations into the event, declined to provide further details of the incident Wednesday.

“We may have investigators in the Bay Area within the next few days,” said NTSB spokesman Keith Holloway. “It is possible that part of the NTSB investigation going forward will be to review (air traffic control) procedures and practices for that airport.”

Jones spoke to this news organization late Wednesday and recounted his return flight from Toronto on Friday after he finished chairing an international conference of insurance regulators who were focusing on climate change.

“It was an uneventful flight until the landing when we descended and were pretty close to touching down, when the jet engines labored loudly and we went into a steep climb,” Jones said. “I recognized something wasn’t quite right and looked around and saw (funny) looks on other passengers’ faces.”

He said the pilot eventually came onto the intercom and “nonchalantly” told passengers they had hit a “little more traffic than they anticipated.”

Jones only found out the real story after reading a Mercury News article Wednesday morning and had a feeling of “surprise and relief.”

“I think air travel generally is pretty safe,” Jones said. “But this has inspired me to spend a night to update my will.”

Matthias Gafni is a Pulitzer Prize winning investigative reporter for the Bay Area News Group. He has reported and edited for Bay Area newspapers since he graduated from UC Davis, covering courts, crime, environment, science, child abuse, education, county and city government, and corruption. A Bay Area native, he loves his Warriors, Giants and 49ers. Send tips to 925-952-5026 or mgafni@bayareanewsgroup.com. Send him an encrypted text on Signal at 408-921-8719.

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